Before diving into this article, readers are encouraged to first read Part I, published here in September 2007 (see Tigrina Times archives). Part I focused on understanding the status of each species in our area and how to tell an Empidonax from an Eastern Wood-Pewee. Now that we know how to rule out a pewee, we can focus on the much more difficult task of distinguishing the Empids. Where do you start?
1) Listen! It should be stated from the beginning that there is no safer means of identifying Empids than by hearing them sing or call. Songs, in particular, are very distinctive and easy to recognize. Call notes take more practice to learn but are also distinctive. For learning visual characters, nothing beats studying a bird that you have already identified with certainty based on vocalizations. A trip to the breeding grounds of each species is the best way to accomplish this. In New Jersey, we are fortunate to have four of the five eastern Empidonax species as breeders. Yellow-bellied does not nest in the state but can be found reliably as close as upstate New York. Studying the structure and plumage of a known-identity bird, and especially appreciating how those features appear to change under varied field conditions, is the most effective way to prepare yourself for studying migrants.
In Cape May, most Empids we see are fall migrants, which do not sing but do occasionally give soft call notes. As with learning plumage features, there is no better way to gain experience with call notes that by studying birds on the breeding grounds where call notes are given more frequently. Listening to tapes or CDs is a great way to brush up on call notes but the descriptions below may also be helpful.
Least Flycatcher – a soft, dry “pwit”
Yellow-bellied Flycatcher – a clear, whistled “pu-EE”; quicker and more sharply rising than Eastern Wood-Pewee’s “puu-eee”; also, a sharp, ringing “pseet” (given mostly on the wintering grounds)
Acadian Flycatcher – a shrill, downward-arched “wsEEw” with a quality like its song; also a sharp, ringing “pseet” (very much like Yellow-bellied but usually lower-pitched and more emphatic)
Alder Flycatcher – a soft, hollow, relatively low-pitched “pip”, not unlike some calls of Carolina Wren; very different from Willow and Least
Willow Flycatcher – a soft, liquid “whit”; very much like Least but slightly longer and lower-pitched; very different from Alder
2) Get as close as possible! It’s hard to overstate just how important it is to get a good view of one of these birds in order to reach a reliable identification. The difference between watching an Empid from 30 feet vs. 15 feet is remarkable. You just have to be close to accurately judge subtleties of structure, color, and plumage condition. Being close also puts you in the best possible situation to hear a soft call note, which is often essential to clinch an identification.
3) Consider size and structure. With practice, it becomes apparent that not all Empids are the same size or have the same proportions. Look especially at bill length and width, head size and shape (rounded, peaked rear crown, etc.), degree of primary projection, and relative length and width of the tail. These features take the most practice to appreciate but are among the most useful. It should be noted, however, that all these characters are somewhat variable so that only extremes are reliable in the field.
4) Overall color. Although color differences between Empids are small, they can provide very useful clues. It should be emphasized that all five species can show distinct washes of yellow on the belly in fresh plumage, but only Yellow-bellied Flycatcher shows an even wash of yellow across the entire underparts, including the throat.
5) Face pattern. Most Empids show some variation of a pale eye ring and pale markings on the lores (the area between the eye and bill). There is considerable variation in the prominence of these features between species but also variation within each species. It is helpful to learn the typical patterns, but it is also wise to use caution when basing your identifications on them. (Never rely on just one field mark, especially when dealing with a group as difficult as Empids.)
6) Try to get the bird in even lighting. Overcast skies or bright shade provide the optimal lighting for looking at an Empid. The strong shadows created by bright sunlight will make it much more difficult to accurately perceive subtleties of color and pattern. And no matter what the lighting, always bear in mind the bird’s surroundings. Reflected light can influence your perception of color.
7) Understand the effects of feather wear. Seeing an Empid in fresh vs. worn plumage can make a big difference in its appearance. Summer birds on the breeding grounds are in moderately worn plumage and tend to look duller overall with less yellow below, duller and paler coloration above, and usually thinner wing bars. In contrast, fresh fall migrants (which along the coast are mostly immatures) look brighter overall, with richer coloration above, more and brighter yellow below, and bolder, often buffy or yellowish-tinged wing bars. During fall migration, a worn adult (adults of all but Acadian Flycatcher molt after migrating to the tropics) will stand out as much duller than the fresh immatures.
8) Don’t be afraid to leave a bird unidentified. The reality is that some non-vocalizing Empids will not be identifiable in the field. This is particularly true of Willow and Alder Flycatchers (which used to be lumped as one species, “Trail’s Flycatcher”). Even the most experienced birders cannot identify every Empid they see, even some seen very well.
| Photo 1 – Least Flycatcher, New Jersey, early October.Being the most common Empid in Cape May, Least Flycatcher provides a good frame of reference. Though difficult to judge, Leasts are smaller than other Empids. Notice the petite structure with slim body and tail, small bill, and short wings. The eye ring is bold (thinnest on the top-front section, like most Empids). The upperparts are gray with a faint olive-brown wash to the crown and back. The short primary projection is a good distinction from other eastern Empids, though this individual shows a longer primary projection than some. Photo by Kevin Karlson. |  |
| Photo 2 – Yellow-bellied Flycatcher, Belize, early December.In many ways, Yellow-bellied Flycatcher is our easiest Empid to identify. They usually look a little chunkier than Leasts, with bigger, rounded heads, shorter tails, and slightly wider bills. Note the distinctly olive-green tone to the upperparts and breast-sides, and the even wash of dull olive-yellow below. Though all Empids may show yellow bellies, Yellow-bellied Flycatcher is the only eastern Empid with an olive-yellow, not white, throat. As a result, the head looks more uniform with little contrast between the throat and cheeks. The eye ring is usually as bold as a Least’s but the pale loral markings weaker. Photo by Michael O’Brien. |  |
| Photo 3 – Yellow-bellied Flycatcher, Belize, early December.The primary projection is usually longer than that of a Least but shorter than Acadian. The very blackish wings with strongly contrasting wing bars are an important distinction from most individuals of the similar Pacific-slope and Cordilleran Flycatchers of the western United States. Note the very weak contrast between the cheeks and throat and the lack of a gray wash on the nape (a trait shared only by Acadian Flycatcher). Photo by Michael O’Brien. |  |
| Photo 4 – Acadian Flycatcher, Maryland, mid-June.Like Yellow-bellied, Acadian is distinctly greenish-backed and lacks a gray wash on the nape. Compared to Yellow-bellied, Acadian looks paler below with a weaker eye ring and bolder loral stripe. Acadian is slightly larger, with a proportionally larger bill, longer tail, and slightly longer primary projection (the longest of any eastern Empid). The head is less rounded than a Yellow-bellied’s, with a flatter forehead and more peaked rear crown. In summer, the plumage is somewhat worn so the belly looks mostly white. In fresh fall plumage, the belly would be clear lemon yellow (not olive-washed) and the throat and breast mostly whitish. Unlike Yellow-bellied and other eastern Empids, Acadians have grayish, not blackish, legs and a pinkish (rather than orange-yellow) mouth lining. However, both of these characters are difficult to see and require extremely close views to judge accurately. Photo by George Jett. |  |
| Photo 5 – Willow Flycatcher, Maryland, late May.Compared to Least Flycatcher, Willow’s upperparts look distinctly brown, like coffee with cream. The nape is washed with gray. Willow is a bulky bird, like Acadian, with a heavy bill (closer to Acadian than Least) and longish primary projection (also closer to Acadian than Least). The eye ring is mostly brown, though it is often paler toward the back edge and sometimes more extensively pale. Photo by Bill Hubick. |  |
| Photo 6 – Alder Flycatcher, Maryland, late May.Very similar to Willow in size and structure but somewhat closer to Least in plumage. Compared to Willow, Alder looks (often distinctly) darker brown above with an olive tinge to the crown and back (more evident in fresh plumage), and often a more contrasting gray nape. The eye ring is thin and usually dusky above the eye but whitish below. On average, Alder’s bill looks smaller and its head has less of a crested look. Due to variation and the very subtle nature of the differences between these species, many non-calling Willow/Alder (“Trail’s”) Flycatchers may not be identifiable to species. This individual shows a relatively short primary projection, approaching Least Flycatcher. Most show slightly longer primaries. Photo by George Jett. |  |
| Photo 7 – Least Flycatcher, Maryland, early September.In strong lighting, notice how Least Flycatcher’s upperparts may appear paler and browner and the eye ring weaker, increasing its similarity to Willow and Alder Flycatchers. This emphasizes why it is important to focus on structure and try to follow the bird until it is in favorable lighting. Notice this bird’s short primary projection, relatively small bill, and overall petite look. Photo by Bill Hubick. |  |